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Next: <a href="s390-Mnemonics.html#s390-Mnemonics" accesskey="n" rel="next">s390 Mnemonics</a>, Up: <a href="s390-Syntax.html#s390-Syntax" accesskey="u" rel="up">s390 Syntax</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p>
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<a name="Register-naming"></a>
<h4 class="subsubsection">9.38.3.1 Register naming</h4>
<a name="index-register-naming_002c-s390"></a>
<a name="index-s390-register-naming"></a>

<p>The <code>as</code> recognizes a number of predefined symbols for the
various processor registers. A register specification in one of the
instruction formats is an unsigned integer between 0 and 15. The specific
instruction and the position of the register in the instruction format
denotes the type of the register. The register symbols are prefixed with
&lsquo;<samp>%</samp>&rsquo;:
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<tr><td><pre class="display">%rN</pre></td><td><pre class="display">the 16 general purpose registers, 0 &lt;= N &lt;= 15</pre></td></tr>
<tr><td><pre class="display">%fN</pre></td><td><pre class="display">the 16 floating point registers, 0 &lt;= N &lt;= 15</pre></td></tr>
<tr><td><pre class="display">%aN</pre></td><td><pre class="display">the 16 access registers, 0 &lt;= N &lt;= 15</pre></td></tr>
<tr><td><pre class="display">%cN</pre></td><td><pre class="display">the 16 control registers, 0 &lt;= N &lt;= 15</pre></td></tr>
<tr><td><pre class="display">%lit</pre></td><td><pre class="display">an alias for the general purpose register %r13</pre></td></tr>
<tr><td><pre class="display">%sp</pre></td><td><pre class="display">an alias for the general purpose register %r15</pre></td></tr>
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